Efforts to relieve the worldwide shortages of protein have included various biosynthesis processes wherein biologically produced single cell proteins (SCP) are obtained by the growth of a variety of microorganisms on a variety of carbon-containing substrates. The carbon and energy sources used as substrates should be available widely, relatively cheap, uniform, and safe in that they do not leave harmful residues in the protein product ultimately obtained by microbial conversion. Petroleum hydrocarbons have been employed as a carbon and energy source, but have faced practical difficulties in the lack of water solubility, in the high consumption of oxygen to assist in the microbial conversion, and allegedly in traces of potentially carcinogenic agents from the petroleum feedstocks entering or adhering to the protein product.
Other processes have centered on the use of oxygenated hydrocarbon derivatives as feedstocks, due to their water solubility and hence ease of handling since microbial conversion processes are essentially conducted under aqueous conditions. Such feedstocks are readily available either from petroleum sources, natural gas sources, various waste/garbage processing and conversion of methane and the like, from fermentation of various grains and the like, destructive distillation of wood, and so on. Such oxygenated hydrocarbons, whatever their source, are widely available and relatively cheap feedstocks for fermentation processes. Advantages accrue in that these feedstocks are partially oxygenated, so that substantially reduced molecular oxygen requirements are involved for the microbial conversion-growth process.
However, another difficult and limiting factor in the commercialization of the single cell protein processes has been the necessity to function at relatively moderate temperatures of about 20.degree. to 50.degree. C., and more preferably not over about 35.degree. C. The microbial conversion is a highly exothermic oxidation reaction with large quantities of heat being produced, which heat must be removed continuously and consistently or risk the overheating of the system and death of the microorganisms, or at least the severe limitation and growth encountered as temperatures rise, and hence severe reductions in efficiencies.
Many processes have concentrated on employment on one or other of the many available yeasts as the microorganism. Many yeasts are available, and the yeast cells generally are slightly larger than a bacteria cell, and sometimes provide easier separation from the fermentation process.
However, the bacteria offer advantages, since higher crude protein contents of the cell are obtained from bacteria as compared to production obtainable from the yeasts in general, the yeasts having higher proportions of nonprotein structural material in their cells. Bacteria usually have a significantly higher true protein content, frequently being nutritionally higher in the important sulfur amino acids and lysine.
Discovery of bacteria with the capability of rapid growth and high productivity rates at relatively high fermentation process temperatures would be distinctly advantageous. High temperature growth operation means less heat to be removed, less cooling apparatus involved, and ultimately relatively smaller amounts of heat needed for sterilization, coagulation, and separation processes. Danger of contamination with other microbes is also greatly reduced. Thermophilic or thermotolerant bacteria are needed for commercialization of the single cell protein process.